Spinal surgery may entail a variety of surgical procedures aimed at, for example, reconstructing a patient's spine following a catastrophic accident or correcting a degenerative condition of the patient's spine. One such system for repairing the spine is using a spinal fixation system including screws and/or other bone anchors that are affixed to structures on a posterior aspect of a vertebra. The screws, for example, may be polyaxial (i.e., multi-planar) or uniplanar (i.e., monoplanar) screws that include a shank having thread features pivotally coupled with a head. The shank is conventionally coupled with the head by extending a distal end of the shank through a top opening in the head such that a proximal enlarged end of the shank resides in a cavity of the head where the cavity has a lower opening that restricts the proximal end portion of the head from extending through the lower opening in the head (i.e., top-loading). The proximal end portion of the shank may then pivot within the cavity to provide movement through one or more planes (e.g., polyaxial, uniplanar).
One or more rods are conventionally affixed to the screw via a top-loading or side-loading arrangement. The rods may be affixed to multiple screws, which may be affixed to pedicles of multiple vertebral bodies. Together, the system of screws and rods may act to stabilize the instrumented vertebral column to aid in the correction or reconstruction of the patient's spine.
While the aforementioned systems are known in the art, there is a need for additional systems and tools to further advance surgical spinal procedures. Such systems and tools will be discussed herein and may include snap-on, bottom-loaded screws, and other bone anchors that provide advantages over techniques, systems, and other bone anchors known in the art.